Improved mode of repairing plumbago crucibles used in melting steel



itlnitrd $111125 @afrnt lBfl1ii r e--.'

NATHAN WASHBURN, OF WORCESTER, MASSACHUSETTS.

Lem-s Patent No. 92,676, dated July 13,1869.)

IMPROVED MODE or REPAIRING FLUMBAG-O ,cnUcIBLEs USED IN vMeta-rive swarm."

The Schedule referred to in these Iletters' Patent and making part of the same To all persons to whom these presents may come two or three heatsof the furnace, before becoming so injured as to be rendered unfit for further use.

Attempts have been made to repair such crucibles,

by dipping them in a fluid-composition of plumbago, mica, and clay, anda patent has recently been taken out -for snch, by William F. Sherman, it being-numbered;87,075; but it has been found, in practice, that this process of repair, though'oftcn useful, cannot be depended on, both on account of the uneven thickness in which the crucible is left afterhaving been dipped, and the fact that spaces containing airTvill be formed in the coating, or between it and the surface to which it may be applied. On heating the crucible, the air will be eiipanded, and cause the coating to scale ofl' or break away from the crucible.

A crucible, after having been charged, and submitted to the action of the powerful heat of a steeI-mclting furnace, generally becomes more or less warped,-

as well as cut away, so as to be of an uneven thickness; that'is to say, it will be reduced more in some places or parts than in others, so that when the restoration is attempted to be effected by the dipping-'pro cess, the crucible, after the carrying out of the same, remains of an uneven thickness.

It is'very important that the proper thickness of the crucible should be preserved, in order that the metal or the flux used while the crucible is being heated, may-not cut through it.

-These plnmbago crucibles, as ordinarily mended,

have been a source of great expense to the makers of cast-steel, for as two or three heats of the furnace, at :the most, would generally destroy them, and as theyusually 00st fi'o'm three to four dollars a piece, the loss per ton, of steel, has been equal to forty dollars.

Steel-makers generally reckon that it costs them,

for every pound of steel produced, about two cents for the crucible. Therefore, it will be seen that any mode of repairing these crucibles, by wllich they will berendered capable of withstanding, for a longer period, the heat of the furnace, must be a great gain to the maker of steel.

My method ofrepairing enables a crucible to be used ,a great number of times; I may state almost an indefinite number. Practice has proved this, as, in-

stead of simply applying to tliecrucible a coating of even thickness, by the process of dipping, thereby leaving the injured crucible of an uneven thickness, I restore the crucible to its normal thickness, and expel from the repairing-composition any and all the 'air which would operate to cause it to scale off under the heat of the furnace.

A crucible that had been-subjected to the dippingprocess and condemned, I have treated by my method, and used it in several heats of the furnace, thus utilizing it to great advantage.

In running twenty-four crucibles, and melting thereby three tons of steel, I find the saving, by my method of repairing, is about seventy-five dollars, and with reference to the dipping-process, I save about fifty dollars, the saving by the dipping-process not exceeding twenty-five dollars.

These results I mention, to exhibit the vast utility of my invention, and the great saving of expense to the manufacturer of.steel.

In carrying out my said invention, I usually employ a composition consisting of Stourbridge clay, firebric'k, and graphite, in equal, or about equal quantities,

These ingredients, after having been ground to a fine powder, are to be' mixed into a paste or mortar, with water. the surface or parts thereof of the crucible required to be thickened. v

After this has been done, the mortar so put on, and while it may be in the process of setting or hardening, should be rubbed, beaten, and worked, by means of a spatula, or other proper implement, so as to thoroughly drive from it any air or air-bubbles, and compress it,

*and finally polish or reduce its outer surface to avcry smooth state;' the smoother the surface the better it will withstand the heat. 7

The dipping-processleaves the surface rough and uneven, and thus renders it more susceptible of injury by the heat of the furnace.

I make no claim to mere dipping a crucible in athin solution of plumbago, mica, and clay, or the equiva- 'lent thereof, forreparation of it.-

What I claim asmy invention, is-- The employment of a composition, as set forth, or its equivalent, inthe form of a mortar, and plastering it on the injured crucible, and working it-when' thereon, so as to expel the air from the said repairing-medium, and bring the crucible to its normal or required thickness, and impart to it a smooth outer surface, as

specified.

N, WASHBURN.

Witnesses:

R. H. EDDY, S. N. PIPER.

This mortar is next to be plastered on' 

